Transformer bushing

ABSTRACT

A transformer bushing extends through an opening in the transformer housing and is movable between a mounted position releasably engaged with said housing and a displaced position disengaged from said housing and retracted from said opening. A coil lead of substantially dead soft material is releasably connected with the bushing, and said coil lead is concertedly movable with said bushing toward the displaced position remaining substantially in said displaced position for subsequent releasable connection with a replacement bushing.

0 Tinned States Patent 1 1 1111 3.8%,523 Farmer et a1. Apr. 9', T974 1TRANSFORMER BUSHING 1,041,123 10/1958 Germany 174/152 75] Inventors:Donald J. Farmer; Charles .B.

Carlson, both of Pine Bluff, Ark. Primary Examiner-Thomas l Kozma [73]Assignee: Central Moloney Inc., Pine Bluff, Attorney, Agent, orFirml(oenig, Senniger, Power Ark. and Leavitt [22] Filed: Mar. 6, 1973[21] Appl. No.: 338,596

[ ABSTRACT [52] Cl gi gj A transformer bushing extends through anopening in [51] i Cl the transformer housing and is movable between a[58] meld of Search 36/90 2 1 mounted position releasably engaged withsaid hous- 174/152 R ing and a displaced position disengaged from saidhousing and retracted from said opening. A coil lead [56] ReferencesCited of substantially dead soft material is releasably'con- UNITEDSTATES PATENTS nected with the bushing, and said coil lead is concert-3,617,968 11/1971 Wakeam 336/223 edly movable with said bushing towardthe displaced 825,882 7/l906 Harper 174/18 position remainingsubstantially in said displaced posi- 2,676,I98 4/1954 Picard [74/152 Rtion for subsequent releasable connection a re- 3,369,166 2/1968 Lake174/152 R x placement bushing FOREIGN PATENTS OR APPLICATIONS 1,383,97911/1964 France 174 152 R 13 Claims, 6 Drawing Figures J TENTEBAPR 919743803523 mm 1 OF 2 TRANSFORMER BUSHING BACKGROUND OF THE INVENTION Thisinvention relates generally to transformers and in particular tobushings used therewith and also to a method of replacing said bushings.

Transformer bushings provided with terminals for connection to anelectrical distribution system have always been susceptible to damageduring handling, shipping, installation and maintenance operations. Inorder to minimize this and to provide an economical and satisfactorysecondary or low voltage bushing, molded synthetic resin bushings with aradially extending mounting flange have been widely used for severalyears. These have been secured by welding to the transformer tank orhousing to provide a sealed feedthrough connection interconnecting theexternal low voltage cables to the transformer core-andcoil unit sealedwithin the tank. While this arrangement has improved breakagecharacteristics over typical porcelain low voltage bushings, thebreakage and damage problem is still a substantial one. Breakage ordamage typically occurs in the field during installation, particularlyduring installation of transformers on pads and underground in vaults orthe like. These damaged bushings cannot be replaced without cutting thewelded flange of the damaged bushing from the transformer tank wall. Asthis cannot be done properly in the field, the entire unit must bereturned to the repair shop or manufacturer for removal of the damagedbushing and replacement thereof. Moreover, even if the damaged bushingcould be cut off in the field, the interior terminal could not bedisconnected from the coil lead and a new bushing connected theretowithout access to the interior of the transformer tank for the manualoperations required.

SUMMARY OF THE INVENTION Among the several objects of the invention arethe provision of a secondary bushing which is secured to the tank wallof the transformer without welding and may be conveniently replaced inthe field without having to gain accessto the interior of thetransformer housing or tank; the provision of a method for convenientlyreplacing a damaged transformer'secondary bushing in the field withoutthe need of access to the interior of the tank; and the provision of atransformer which is rugged in construction, economical to produce, andreliable in operation. Other objects and features will be in partapparent and in part pointed out hereinafter.

Briefly, the present invention comprises a transformer having a housingwith an opening therein, a bushing releasably engaged with said housingand extending through said opening, and a transformer coil lead ofsubstantially dead soft material releasably connected with said bushing,said coil lead being concertedly movable with said bushing through saidopening and being adapted to remain substantially in the displacedposition for subsequent connection with a replacement bushing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a portion of atransformer tank shown in section and to which is secured a secondarybushing interconnecting an internal coil lead with an external terminalin accordance with the present inventron;

FIG. 2 is a view similar to FIG. II, but with the bhshing showndisengaged from the tank and in a displaced position for bushingreplacement;

FIG. 3 is a plan view of the bushing of FIG. 1;

FIG. 4 is a sectional view taken along line 4-4 of FIG. 3;

FIG. 5 is an enlarged fragmentary view of the transformer coil lead andconnecting means of FIG. l; and

FIG. 6 is an enlarged fragmentary view showing the connecting means ofFIG. 6 partially in cross section.

Corresponding reference characters indicate corre sponding partsthroughout the several views of the drawings.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings andin particular to FIGS. l and 2, a transformer, indicated generally at l,is provided with an enclosed tank or housing 2 having a wall or sideportion 3 in which a terminal or bushingreceiving aperture or opening 4is provided, and a plurality of threaded mounting studs or bolts 5 arefixedly connected by suitable means, such as welding, to the exteriorside or portion of said housing. wall about said opening. Referring nowalso to FIGS. 3 and 4, a molded or cast low voltage or secondary bushing6 is provided with a metallic conductor or rod member or stud 7 havingthreaded exterior and interior end or connecting portions 8, 9 with themidportion of said stud bonded to a body portion 10 of a suitablesynthetic resin material, such as an epoxy resin. A typical secondaryterminal 8, shown in phantom is threadedly engaged on the extension endof conductor 7. The body portion 10 of the bushing 6 is provided with aradially extending mounting flange 11 in which mounting holes orapertures 12 are respectively provided for receiving the housingmounting bolts 5.

When the bushing 6 is secured to the housing wall 3, as shown in FIG. I,the mounting bolts 5 are received in the bushing apertures 12, and'aplurality of nuts 13 are threadedly received on said mounting bolts indisplacement preventing engagement with the bushing mounting flange llllurging it toward a mounted sealed position in engagement with thehousing wall 3. Asuitable resilient gasket or sealing member 14 of bunaor the like is sealably engaged between the bushing flange Ill and thehousing side wall 3, while a coil lead or strap member H5 is connectedbetween the interior end of conductor 7 and the low voltage winding of atransformer core and coil unit ll6,ll7 disposed within the housing 2 ina manner well known in the art.

The coil lead 15, as also shown in FIGS. 5 and 6, is preferably formedof one or more leads or laminated strips or layers 18 of aluminum of BC.(electrical conductor) grade which has a physical characteristic ofbeing substantially dead soft thereby affording sufficient rigidity toremain substantially in the static position in which it is placed andyet having sufficient flexibility to be movable to another staticposition. As previously mentioned, one end of the lead is connected tothe transformer coil 17, and a block-shaped terminal 19 is fixedlyconnected by suitable means, such as the weld 20, to the other end ofsaid coil lead. Terminal 19 is provided with a threaded blind bore 21therein in which the internal end 9 of the bushing 6 is threadedlyreceived, and in order to maintain such threaded engagement between saidbushing internal end terminal block bore, a locking member, such as ajam or lock nut 22, is threadedly received on said bushing interior endin locking engagement with the terminal 19. It should be noted that theterminal 19 is predeterminately sized for movement through the opening 4in the housing side wall 3, as discussed fully hereinafter.

In the event the bushing 6 is damaged, it can easily be disassembledfrom said transformer and a replacement bushing assembled theretowithout returning said transformer to the manufacturer and withoutdisassembling the transformer 2 to gain access to the interior thereof.For instance, if the bushing 6 is damaged, the nuts 13 are manuallythreadedly disengaged from the housing studs 5, and the bushing 6 isthenmanually moved from its mounted position in engagement with the housingwall 3 toward a displaced or retracted position, as shown in FIG. 2,wherein the bushing mounting holes 12 are displaced from said housingstuds and at least a portion of the interior end portion 9 of saidbushing is retracted or moved outwardly through the housing opening 4.When the bushing 6 is moved toward its displaced position, the coil lead15 and block terminal 19 are'concertedly movable'therewit h so that atleast a portion of said block terminal extends through the housingopening 4. With the bushing 6 and terminal 19 in their displacedpositions, as described above, tools or wrenches (now shown) may bemanually inserted into driving engagement with the block terminal 19 andlock nut 22 to move said lock nut toward a position disengaged from saidblock terminal, i.e., out of locking engagement therewith. Thereafter,the bushing 6 is manually rotated to effect the threaded disengagementof the bushing interior end 9 from the block terminal bore 21 and thedisplacement of said bushing from the coil lead 15. However, while it ispreferred to retain a grip on the block terminal 19 manually or with awrench etc., until the replacement bushing stud is threaded into the jamnut and block terminal, even if the coil lead end is released the coillead and block terminal will remain substantially in the displacedposition thereof for subsequent assembly with a replacement bushing dueto the dead soft physical characteristic of the aluminum coil lead 15.

Upon the disassembly of the damaged bushing, as above described, thelock nut 22 is threaded onto the end 9 of a replacement-bushing, and thethreaded interior end 9 of the replacement bushing then is manuallythreaded into engagement with the bore 21 of block terminal 19 in itsdisplaced position and the lock nut 22 is retightened. The replacementbushing, terminal 19, and coil lead 15 are concertedly inwardly movedtoward their mounted positions aligning the bushing mounting holes 12with the housing studs 5 to position the replacement bushing in mountingengagement with the housing wall 3. The nuts 13 are then againthreadedly re-engaged with the housing studs 5 in displacementpreventing engagement with the mounting flange 11.

The block terminal 19, preferably formed from a relatively hard and hightensile strength aluminum, such as alloy 606], used in conjunction withthe aluminum coil lead 15 has certain distinct advantages. Hitherto,particularly if the bushing stud were of bronze or brass, a copper coillead would have to be used to interconnect the interior bushing stud end9 to the low voltage coil. Aluminum coil leads, because of cold flowcharacteristics tend to develop a relatively high resistance connectionat the junction where the coil lead end is conventionally secured by anut and washer to the bushing stud end 9, if the latter is formed ofbronze or brass. This could result in a thermal runaway condition andfailure of the unit. The use of the block terminal 19 of this hardertype aluminum permits the use of the more economical aluminum coil leadswithout regard to the metal used for the bushing stud and avoids coldflow and possible thermal runaway problems. The electrical resistance ofthe threaded connection of block terminal 19 and stud end 9 isadvantageously low and cold flow is avoided. Moreover, the mass andsurface area of the block terminal 19 has advantageous heat flow anddissipation characteristics.

From the foregoing, it is now apparent that a novel transformer 1 andbushing 6 construction and a novel method of assembly thereof meetingthe objects and advantageous features set forth hereinabove, as well asothers, are disclosed.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:

l. A transformer comprising an-assembled housing having an openingtherein, a core and coil assembly disposed within said housing, abushing extending through said opening and movable between a mountedposition releasably engaged with said housing and a dipslaced positiondisengaged from said housing and retracted from said opening, and a coillead of substantially dead soft conductor material releasably connectedwith said bushing, said coil lead being concertedly movable with saidbushing through said opening toward the displaced position and adaptedto remain substantially in said displaced position for subsequentreleasable connection with a replacement bushing in the event saidfirstnamed bushing is damaged.

2. A transformer according to claim 1, wherein said coil lead isaluminum.

3. A transformer according to claim 1, wherein said coil lead includes aplurality of laminated strip members, one end of said strip membersbeing conductively connected with said coil and the other end thereofbeing releasably connected with said bushing.

4. A transformer according to claim 1, wherein said coil lead includesterminal means releasably connected with said bushing and sized formovement therewith through said opening.

5. A transformer according to claim 1, wherein said coil lead includes aplurality of laminated strip members having one end thereof conductivelyconnected with said coil, and terminal means conductively connected withthe other end of said strip members and relasably connected with saidbushing, said terminal means being sized for movement through saidopening.

6. A transformer according to claim 1, wherein said bushing includes aninsulating portion extending substantially coaxially through saidopening and releasably connected with said housing, and a conductivestud extending through said insulating portion and having an end portioninteriorly of said housing and releasably engaged with said coil lead.

7. A transformer according to claim 6, wherein said insulating portionincludes a radially extending mounting flange connected in releasableengagement with said housing exteriorly thereof and about said opening.

8. A transformer according to claim 1, comprising a plurality ofmounting studs secured to said housing exteriorly thereof about saidopening, said bushing including a mounting flange for engagement withsaid housing about said opening, a plurality of mounting holes in saidmounting flange and received on said studs, and a plurality of nutsthreadedlyreceived on said studs and engaged with said mounting flangeurging it into engagement with said housing.

9. A transformer according to claim 1, wherein said bushing includes aninsulating portion extending through said opening, a mounting flangeintegral with said insulating portion and extending substantiallyradially thereof for engagement with said housing about said opening, aplurality of mounting holes in said mounting flange, and a conductiverod member extending through said insulating portion and having opposedend portions interiorly and exteriorly of said housing, respectively,said interior end portion being releasably connected with said coillead, a plurality of threaded studs engaged with said housing about saidopening and received in said mounting holes, and a plurality of nutsthreadedly received on said studs and engaged with said mounting flangeurging it toward engagement with said housing about said opening.

10. A transformer according to claim 6, wherein said coil lead includesterminal means releasably connected with said interior end portion ofsaid bushing stud, said terminal means being predeterminately sized formovement through said opening.

11. A transformer according to claim 10, wherein said coil lead includesa plurality of interconnected strip members, one end of said stripmembers being conductively connected with said coil and the other end ofsaid strip members being connected with said terminal means.

12. A transformer according to claim 11, wherein said interior end ofsaid conductive stud si threaded, said coil lead is formed ofsubstantially dead soft aluminum and said terminal means comprises ablock of relatively high tensile strength aluminum having a threadedbore therein for threaded engagement with said stud interior end.

13. A transformer comprising an enclosed housing having a wall portion,an opening in said wall portion, a plurality of threaded studs securedto said wall portion about said opening, a bushing including aninsulating portion extending substantially through said opening, aflange integral with said insulating portion and extending substantiallyradially thereof for engagement with said housing about said opening, aplurality of mounting apertures in said flange in which said studs arerespectively received, and a conductive rod member extending throughsaid insulating portion and having threaded ends interiorly andexteriorly of said housing, a plurality of nuts respectively threadedlyreceived on said studs and engaged with said flange urging it toward amounting position in engagement with said wall portion about saidopening, said bushing being movable toward a displaced positiondisengaged from said housing and retracted from said opening upon theremoval of said nuts from engagement with said studs and said flange, acore and coil assembly disposed within said housing, a coil leadincluding a plurality of laminated interconnected strips of a conductivemetal having a substantially dead soft physical characteristic andopposite end portions, one of said end portions being conductivelyconnected with said coil, a terminal conductively connected with theother of said end portions, a threaded bore in said terminal threadedlyengaged with the interior end of said rod member, and a lock nutthreadedly received on said interior end of said rod member in lockingengagementwith said terminal, said terminal, and lead being concertedlymov able with said bushing toward the displaced position wherein atleast a portion of said terminal protrudes through said openingexteriorly of said housing and remains substantially in the displacedposition due to the substantially dead soft physical characteristic ofsaid coil lead for subsequent threaded engagement with a replacementbushing upon the threaded disengagement of said interior end of said rodmember from said terminal bore in the event said first-named bushing isdamaged.

1. A transformer comprising an assembled housing having an openingtherein, a core and coil assembly disposed within said housing, abushing extending through said opening and movable between a mountedposition releasably engaged with said housing and a displaced positiondisengaged from said housing and retracted from said opening, and a coillead of substantially dead soft conductor material releasably connectedwith said bushing, said coil lead being concertedly movable with saidbushing through said opening toward the displaced position and adaptedto remain substantially in said displaced position for subsequentreleasable connection with a replacement bushing in the event saidfirst-named bushing is damaged.
 2. A transformer according to claim 1,wherein said coil lead is aluminum.
 3. A transformer according to claim1, wherein said coil lead includes a plurality of laminated stripmembers, one end of said strip members being conductively connected withsaid coil and the other end thereof being releasably connected with saidbushing.
 4. A transformer according to claim 1, wherein said coil leadincludes terminal means releasably connected with said bushing and sizedfor movement therewith through said opening.
 5. A transformer accordingto claim 1, wherein said coil lead includes a plurality of laminatedstrip members having one end thereof conductively connected with saidcoil, and terminal means conductively connected with the other end ofsaid strip members and releasably connected with said bushing, saidterminal means being sized for movement through said opening.
 6. Atransformer according to claim 1, wherein said bushing includes aninsulating portion extending substantially coaxially through saidopening and releasably connected with said housing, and a conductivestud extending through said insulating portion and having an end portioninteriorly of said housing and releasably engaged with said coil lead.7. A transformer according to claim 6, wherein said insulating portionincludes a radially extending mounting flange connected in releasableengagement with said housing exteriorly thereof and about said opening.8. A transformer according to claim 1, comprising a plurality ofmounting studs secured to said housing exteriorly thereof about saidopening, said bushing including a mounting flange for engagement withsaid housing about said opening, a plurality of mounting holes in saidmounting flange and received on said studs, and a plurality of nutsthreadedly received on said studs and engaged with said mounting flangeurging it into engagement with said housing.
 9. A transformer accordingto claim 1, wherein said bushing includes an insulating portionextending through said opening, a mounting flange integral with saidinsulating portion and extending substantially radially thereof forengagement with said housing about said opening, a plurality of mountingholes in said mounting flange, and a conductive rod member extendingthrough said insulating portion and having opposed end portionsinteriorly and exteriorly of said housing, respectively, said interiorend portion being releasably connected with said coil lead, a pluralityof threaded studs engaged with said housing about said opening andreceived in said mounting holes, and a plurality of nuts threadedlyreceived on saId studs and engaged with said mounting flange urging ittoward engagement with said housing about said opening.
 10. Atransformer according to claim 6, wherein said coil lead includesterminal means releasably connected with said interior end portion ofsaid bushing stud, said terminal means being predeterminately sized formovement through said opening.
 11. A transformer according to claim 10,wherein said coil lead includes a plurality of interconnected stripmembers, one end of said strip members being conductively connected withsaid coil and the other end of said strip members being connected withsaid terminal means.
 12. A transformer according to claim 11, whereinsaid interior end of said conductive stud si threaded, said coil lead isformed of substantially dead soft aluminum and said terminal meanscomprises a block of relatively high tensile strength aluminum having athreaded bore therein for threaded engagement with said stud interiorend.
 13. A transformer comprising an enclosed housing having a wallportion, an opening in said wall portion, a plurality of threaded studssecured to said wall portion about said opening, a bushing including aninsulating portion extending substantially through said opening, aflange integral with said insulating portion and extending substantiallyradially thereof for engagement with said housing about said opening, aplurality of mounting apertures in said flange in which said studs arerespectively received, and a conductive rod member extending throughsaid insulating portion and having threaded ends interiorly andexteriorly of said housing, a plurality of nuts respectively threadedlyreceived on said studs and engaged with said flange urging it toward amounting position in engagement with said wall portion about saidopening, said bushing being movable toward a displaced positiondisengaged from said housing and retracted from said opening upon theremoval of said nuts from engagement with said studs and said flange, acore and coil assembly disposed within said housing, a coil leadincluding a plurality of laminated interconnected strips of a conductivemetal having a substantially dead soft physical characteristic andopposite end portions, one of said end portions being conductivelyconnected with said coil, a terminal conductively connected with theother of said end portions, a threaded bore in said terminal threadedlyengaged with the interior end of said rod member, and a lock nutthreadedly received on said interior end of said rod member in lockingengagement with said terminal, said terminal and lead being concertedlymovable with said bushing toward the displaced position wherein at leasta portion of said terminal protrudes through said opening exteriorly ofsaid housing and remains substantially in the displaced position due tothe substantially dead soft physical characteristic of said coil leadfor subsequent threaded engagement with a replacement bushing upon thethreaded disengagement of said interior end of said rod member from saidterminal bore in the event said first-named bushing is damaged.